<?php
/**
 * PHPExcel
 *
 * Copyright (c) 2006 - 2013 PHPExcel
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * @category   PHPExcel
 * @package    PHPExcel_Shared_Trend
 * @copyright  Copyright (c) 2006 - 2013 PHPExcel (http://www.codeplex.com/PHPExcel)
 * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt	LGPL
 * @version    1.7.9, 2013-06-02
 */


require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/linearBestFitClass.php';
require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/logarithmicBestFitClass.php';
require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/exponentialBestFitClass.php';
require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/powerBestFitClass.php';
require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/polynomialBestFitClass.php';


/**
 * PHPExcel_trendClass
 *
 * @category   PHPExcel
 * @package    PHPExcel_Shared_Trend
 * @copyright  Copyright (c) 2006 - 2013 PHPExcel (http://www.codeplex.com/PHPExcel)
 */
class trendClass {
	const TREND_LINEAR = 'Linear';
	const TREND_LOGARITHMIC = 'Logarithmic';
	const TREND_EXPONENTIAL = 'Exponential';
	const TREND_POWER = 'Power';
	const TREND_POLYNOMIAL_2 = 'Polynomial_2';
	const TREND_POLYNOMIAL_3 = 'Polynomial_3';
	const TREND_POLYNOMIAL_4 = 'Polynomial_4';
	const TREND_POLYNOMIAL_5 = 'Polynomial_5';
	const TREND_POLYNOMIAL_6 = 'Polynomial_6';
	const TREND_BEST_FIT = 'Bestfit';
	const TREND_BEST_FIT_NO_POLY = 'Bestfit_no_Polynomials';

	/**
	 * Names of the best-fit trend analysis methods
	 *
	 * @var string[]
	 **/
	private static $_trendTypes = array(
			self::TREND_LINEAR,
			self::TREND_LOGARITHMIC,
			self::TREND_EXPONENTIAL,
			self::TREND_POWER
	);
	/**
	 * Names of the best-fit trend polynomial orders
	 *
	 * @var string[]
	 **/
	private static $_trendTypePolyOrders = array(
			self::TREND_POLYNOMIAL_2,
			self::TREND_POLYNOMIAL_3,
			self::TREND_POLYNOMIAL_4,
			self::TREND_POLYNOMIAL_5,
			self::TREND_POLYNOMIAL_6
	);

	/**
	 * Cached results for each method when trying to identify which provides the best fit
	 *
	 * @var PHPExcel_Best_Fit[]
	 **/
	private static $_trendCache = array();


	public static function calculate($trendType = self::TREND_BEST_FIT, $yValues, $xValues = array(), $const = true) {
		//	Calculate number of points in each dataset
		$nY = count($yValues);
		$nX = count($xValues);

		//	Define X Values if necessary
		if ($nX == 0)
		{
			$xValues = range(1, $nY);
			$nX = $nY;
		}
		elseif ($nY != $nX)
		{
			//	Ensure both arrays of points are the same size
			trigger_error("trend(): Number of elements in coordinate arrays do not match.", E_USER_ERROR);
		}

		$key = md5($trendType . $const . serialize($yValues) . serialize($xValues));
		//	Determine which trend method has been requested
		switch ($trendType)
		{
			//	Instantiate and return the class for the requested trend method
			case self::TREND_LINEAR :
			case self::TREND_LOGARITHMIC :
			case self::TREND_EXPONENTIAL :
			case self::TREND_POWER :
				if (!isset(self::$_trendCache[$key]))
				{
					$className = 'PHPExcel_' . $trendType . '_Best_Fit';
					self::$_trendCache[$key] = new $className($yValues, $xValues, $const);
				}

				return self::$_trendCache[$key];
				break;
			case self::TREND_POLYNOMIAL_2    :
			case self::TREND_POLYNOMIAL_3    :
			case self::TREND_POLYNOMIAL_4    :
			case self::TREND_POLYNOMIAL_5    :
			case self::TREND_POLYNOMIAL_6    :
				if (!isset(self::$_trendCache[$key]))
				{
					$order = substr($trendType, -1);
					self::$_trendCache[$key] = new PHPExcel_Polynomial_Best_Fit($order, $yValues, $xValues, $const);
				}

				return self::$_trendCache[$key];
				break;
			case self::TREND_BEST_FIT            :
			case self::TREND_BEST_FIT_NO_POLY    :
				//	If the request is to determine the best fit regression, then we test each trend line in turn
				//	Start by generating an instance of each available trend method
				foreach (self::$_trendTypes as $trendMethod)
				{
					$className = 'PHPExcel_' . $trendMethod . 'BestFit';
					$bestFit[$trendMethod] = new $className($yValues, $xValues, $const);
					$bestFitValue[$trendMethod] = $bestFit[$trendMethod]->getGoodnessOfFit();
				}
				if ($trendType != self::TREND_BEST_FIT_NO_POLY)
				{
					foreach (self::$_trendTypePolyOrders as $trendMethod)
					{
						$order = substr($trendMethod, -1);
						$bestFit[$trendMethod] = new PHPExcel_Polynomial_Best_Fit($order, $yValues, $xValues, $const);
						if ($bestFit[$trendMethod]->getError())
						{
							unset($bestFit[$trendMethod]);
						}
						else
						{
							$bestFitValue[$trendMethod] = $bestFit[$trendMethod]->getGoodnessOfFit();
						}
					}
				}
				//	Determine which of our trend lines is the best fit, and then we return the instance of that trend class
				arsort($bestFitValue);
				$bestFitType = key($bestFitValue);

				return $bestFit[$bestFitType];
				break;
			default    :
				return false;
		}
	} //	function calculate()

} //	class trendClass
